For best accuracy I suggest NSing the cases with either a bushing die or a Lee collet die. A standard FL die "partial resizing" can warp the thin necks when the expander is pulled through the unsupported neck. A FL die can be used successfully if the cases are deprimed as a separate step then partial sized to the depth of the seated bullet leaving the remainder of the neck fitted to the chamber neck. With a case up into the FL die size just that much then adjust the expander up until it just stops at the sized neck and then back off one turn of the stem. That way the neck can be supported by the die and will not be warped crooked.
I use the Hornady 45 gr Hornet bullets almost exclusively in my Hornets. I've found loading them over 12.5 gr Lil'Gun in R-P cases with a SP primer is an excellent load and should run 2700 - 2800 fps out of your 20" barrel. Accuracy has always been excellent, as good as the rifle will shoot. In pressure testing (21" Contender Carbine barrel via Oehler m43 PBL) Winchester factory 46 JHP 22 Hornet ran 28,300 psi at 2514 fps. The 12.5 gr Lil'Gun under the 45 gr Hornady ran 22,800 psi at 2704 fps with the 10 shot test group measuring .585" ctc at 100 yards..